The pilot and his passenger were killed instantly when the airplane crashed. Their identities have not been confirmed, Harris County medical examiners said Sunday.

"Our condolences go out to the families," LeBaron said. "It's a tough time for people when this happens."

Federal Aviation Administration records show the airplane was owned by an Austin-based company that could not be reached for comment. LeBaron did not know the plane's destination.

Investigators began arriving Sunday to try to piece together clues. The tail was still visible behind the yellow police tape but the aircraft's passenger section was destroyed in the fire.

"We haven't been out here very long," LeBaron said. "Everything is very preliminary."

During their investigation, the NTSB officials will examine the pilot's background. The airplane and its maintenance logs also will be scrutinized. Representatives from the companies that manufactured the airframe and the engine also were at the crash site.

"We'll look at the engine and determine if there was an issue with it," LeBaron said. "We'll go through all the flight controls on the airplane."

The third part of the NTSB inquiry will address environmental issues — such as the weather, runway conditions and whether other aircraft were in the area at the time.

The private airplane did not have a cockpit recording device but investigators hoped to find a global positioning system on board that might yield some information.

"It's through tragedies like this that we gain knowledge to make flying safer for all of us," LeBaron said.